athoirs
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| posted on 5/12/07 at 04:25 PM |
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Inboard suspension
Hi Guys.
During this winters rebuild I have been toying with the idea of putting in inboard front suspension on my Indy, for the following reasons.
Rising rate suspension.
Get rid of the shock being mid wishbone ( not good)
Reduce the unsprung mass
Fit an inboard anti roll bar.
I have already made up some new wishbones, but before I start designing the rocker (ratio?) and shock mounts has anyone done this already to an
Indy??
I know the new indy has Inboard shocks although I am not sure about the way that’s designed. MNR looks good so I think I will more like that.
thanks
Andy
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Mr Whippy
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| posted on 5/12/07 at 04:29 PM |
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Reduce the unsprung mass - will increase due to weight of pushrod and link cam
Fit an inboard anti roll bar - this might end up very stiff if your not careful
quote:
Originally posted by athoirs
Hi Guys.
During this winters rebuild I have been toying with the idea of putting in inboard front suspension on my Indy, for the following reasons.
Rising rate suspension.
Get rid of the shock being mid wishbone ( not good)
Reduce the unsprung mass
Fit an inboard anti roll bar.
I have already made up some new wishbones, but before I start designing the rocker (ratio?) and shock mounts has anyone done this already to an
Indy??
I know the new indy has Inboard shocks although I am not sure about the way that’s designed. MNR looks good so I think I will more like that.
thanks
Andy
[Edited on 5/12/07 by Mr Whippy]
Fame is when your old car is plastered all over the internet
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pewe
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| posted on 5/12/07 at 05:04 PM |
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Formula 27s (F27 as they are now known) have these. I've a set of plans you can have a butchers at if it will help?
Cheers, Pewe 
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worX
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| posted on 5/12/07 at 05:05 PM |
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Are you sure about that? I would go along with Andy and say that the removal of his shocks/springs and placement inboard, and the use of a pushrod
would definitely reduce the unsprung weight...
And yes the front end may end up stiff with a front ARB but that's why most people make them adjustable...
quote:
Originally posted by Mr Whippy
Reduce the unsprung mass - will increase due to weight of pushrod and link cam
Fit an inboard anti roll bar - this might end up very stiff if your not careful
quote:
Originally posted by athoirs
Hi Guys.
During this winters rebuild I have been toying with the idea of putting in inboard front suspension on my Indy, for the following reasons.
Rising rate suspension.
Get rid of the shock being mid wishbone ( not good)
Reduce the unsprung mass
Fit an inboard anti roll bar.
I have already made up some new wishbones, but before I start designing the rocker (ratio?) and shock mounts has anyone done this already to an
Indy??
I know the new indy has Inboard shocks although I am not sure about the way that’s designed. MNR looks good so I think I will more like that.
thanks
Andy
[Edited on 5/12/07 by Mr Whippy]
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lsdweb
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| posted on 5/12/07 at 05:12 PM |
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Not a '7' and not a pushrod system in the way I think you are suggesting but
this may give you some inspiration.
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zilspeed
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| posted on 5/12/07 at 06:15 PM |
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When I was over at the Rotor workshop checking out the JT7 - ooh that's let the cat out of the bag - I had a bit of a eureka moment regarding
rocker ratios etc.
The way Graham has designed it, uses something like a 2.5 / 3 : 1 ratio so that 1 unit of wheel deflection equals 3 units of damper deflection.
To me, that has two benefits.
1) You have greater control over what the damper does due to having the further travel. Think of the opposite rocker ratio and that will make
wonderfull sense.
2) Spring rates - because of the rocker ratio, the JT7 uses relatively soft springing along with big damper travel. The really good bit about this
setup is that 3 units of spring rate increase or decrease is only seen as 1 at the wheel. So for example you could be out by 75 lb/in on the damper
and that would translate to 25 lb/in at the wheel. That's closer than most people would get I reckon.
Any design not using these advantages is missing out on two very big tricks and must by default be for show rather than for effect.
P.S. Look at single seaters and see this in action.
P.P.S. Look at all the kit cars with the opposite rocker ratios...
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SeaBass
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| posted on 5/12/07 at 06:30 PM |
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JT7 in yellow? Or is he doing something new?
Cheers
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zilspeed
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| posted on 5/12/07 at 07:08 PM |
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He's doing several new things, but it was the blue JT7 I was checking out.
It really suits blue so much better. If only I had the cash I would be through there doing a deal right now.
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Mave
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| posted on 5/12/07 at 07:34 PM |
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I'm thinking about the same thing for my Indy. Partly because I just think it looks nicer. But other than that, I've already done some
analysis; it's possible to have a slightly rising rate (good thing!).
For inspiration; you could do worse than looking at the suspension system that Freestyle makes for Caterham; that's a bolt-on affair; the rocker
attaches to the chassis shock mount.
Let me know if you proceed, and in what way.
Marcel
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britishtrident
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| posted on 5/12/07 at 09:41 PM |
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This something you really have to think carefully about a few things. To illustrate the first point I am going to borrow a quote from another forum
(AtlasF1) where chassis stiffness was being discuss Quote NRoshier
" I think Greg was making the point that the chassis may be easily stiff enough as a structure, but stiffness is easily lost is the
suspension pickup/mounts. When I interviewed Ron Tauranac he clearly stated that this was the case and that lots of attention had to be paid to the
suspension/damper mounts. "
for full thread see http://forums.autosport.com/showthread.php?s=9ea20dce58f453fa514066f181e420a6&threadid=98078
With any kind of inboard suspension the loads are much higher than conventional suspension. Consider simple top rocker top wishbones as on the Lotus
25/33 the rocker pivots are taking at least twice the reaction load of the original spring mounting AND the chassis spring/damper mounting also has
a load, this translates as loss of torsional stiffness for little or no gain in unsprung inertia. Forget about unsprung weight it is unsprung
inertia that matters.
The alternatives are push rod or pull rod systems, with these systems the damper and spring can be smaller and lighter BUT the chassis
mounting stiffness problem becomes even greater. Any single seater or clubman racers that use this type of suspension layout use much more complex
spaceframes than the Indy chassis. The Indy chassis is like the original Lotus 7 a sparse spaceframe it has few members and little triangulation. A
complex spaceframe has lots of very short structural members which are heavily triangulated.
The real advantage of inboard suspension is aerodynamic.
[Edited on 5/12/07 by britishtrident]
[Edited on 5/12/07 by britishtrident]
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Mr Whippy
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| posted on 6/12/07 at 08:41 AM |
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Yes.
Remember the un-sprung weight is not the physical weight of the components (in both cases the shocker is supported by the chassis) but the mass that
has to actually move.
therefore un-sprung mass =
1) Damper + Spring + wishbones + wheels
or
2) Damper + Spring + Cam + Pushrod + wishbones +Wheels...
quote:
Originally posted by worX
Are you sure about that? I would go along with Andy and say that the removal of his shocks/springs and placement inboard, and the use of a pushrod
would definitely reduce the unsprung weight...
And yes the front end may end up stiff with a front ARB but that's why most people make them adjustable...
quote:
Originally posted by Mr Whippy
Reduce the unsprung mass - will increase due to weight of pushrod and link cam
Fit an inboard anti roll bar - this might end up very stiff if your not careful
quote:
Originally posted by athoirs
Hi Guys.
During this winters rebuild I have been toying with the idea of putting in inboard front suspension on my Indy, for the following reasons.
Rising rate suspension.
Get rid of the shock being mid wishbone ( not good)
Reduce the unsprung mass
Fit an inboard anti roll bar.
I have already made up some new wishbones, but before I start designing the rocker (ratio?) and shock mounts has anyone done this already to an
Indy??
I know the new indy has Inboard shocks although I am not sure about the way that’s designed. MNR looks good so I think I will more like that.
thanks
Andy
[Edited on 5/12/07 by Mr Whippy]
Fame is when your old car is plastered all over the internet
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